One is often led to use it by mistake (6)
I believe the answer is:
eraser
'one' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for eraser that I've seen before include "destroyer" , "(Pencil, ink) rubber" , "A student's rubber, or the one who uses it" , "Rubber for removing marks" , "One removes writing" .)